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This paper presents an online, accurate and easy to use method for metal transfer mode classification using the input electrical impedance of arc welding as the signature. The records of the input electrical impedance are obtained by processing the welding voltage and current signals picked up at the output terminal of a welding machine. Similar to a typical linear electrical circuit consisting of a resistor, an inductor and a capacitor connected in series, the real and imaginary part of the input electrical impedance represents the combination of these electrical elements in the arc welding. Their variations directly reflect the switching among the metal transfer modes. A few experiments were conducted to confirm the above working principle and correlations between the input electrical impedance of arc welding and metal transfer. The results were then used to develop a method for online classification of metal transfer modes.

We reported a new method based on the input electrical impedance of a welding system to measure the resistance of the welding system for the arc power calculation in fusion welding. This impedance can be obtained by dividing the measured voltage to current in their analytic form. Two time recorded waveforms, namely, resistance and reactance of impedance, are therefore calculated. Theoretically, the resistance used for arc power calculation is obtained by dividing measured voltage to current directly without considering the influence of inductance. Through experimental studies, we confirm that the error of arc power calculation incurred by the influence of inductance can range from 2 to 10% depending on the welding voltage and current setting. Since the proposed method can obtain the resistance of the welding system without the influence of inductance, it is a better approach as compared with the current method to obtain the accurate resistance and then arc power.